Characteristics of virulent vibrio parahaemolyticus isolated from Oregon and Washington

Virulence Genes Analysis of Vibrio parahaemolyticus and Anti-vibrio Activity of the Citrus Extracts

Vibrio parahaemolyticus (VP) is a marine bacterium that opportunistically caused foodborne gastroenteritis in human and some diseases in marine animals. The isolated strain of V. parahaemolyticus WS001 from Samut Sakhon, Thailand has a presence of ldh (~ 450 bp) toxA (~ 333 bp) and toxB (~ 1269 bp) genes which showed pathogenicity in shrimp. This strain is suspected as low pathogenicity in human due to the lack of tdh and trh genes for encoding thermostable direct hemolysin (TDH) and TDH-related hemolysin (TRH), respectively. The shrimp pathogenic strain was tested and revealed the multi-antibiotic resistances but was susceptible to norfloxacin (10 μg/ml). Citrus peel extracts were examined because they are rich in bioactive compounds such as saponins, tannins, flavonoids, steroids, and alkaloids that are effective in anti-VP activities. The ethanolic peel extracts of Citrus aurantifolia (Christm.) Swingle and Citrus hystrix DC. were found to be more anti-VP effect than other solvent extracts by Agar disc diffusion method at an optimum concentration of 50 mg/ml and Broth micro-dilution method (MICs of 50-100 mg/ml and MBCs of 100-200 mg/ml). Thus, C. aurantifolia (Christm.) Swingle peel extract was a distinctive candidate for the development of alternative natural agent to control the spreading of diseases in shrimp.

Abundance, antimicrobial resistance, and virulence of pathogenic Vibrio strains from molluscan shellfish farms along the Korean coast

To reduce the outbreaks caused by the major pathogenic Vibrio species, V. parahaemolyticus, V. vulnificus, and V. cholerae, the distribution, antibiotic resistance, and virulence of these Vibrio strains were monitored in shellfish and seawater along the Korean coast. Among the Vibrio strains, V. parahaemolyticus was the most abundant species; during summer, this strain showed a substantial increase that correlated with the water temperature. Although >99.0% of the Vibrio species isolates were sensitive to seven antimicrobials recommended by the Center for Disease Control and Prevention for the treatment of Vibrio infections, multiple-antibiotic resistance to at least three antimicrobials was found in 14.3% to 50.0% of each Vibrio species. Among V. parahaemolyticus isolates, 14.3% were positive for the trh gene, whereas only 1% was positive for the tdh gene. These results should aid in implementing proper precautions to avoid potential human health risks associated with exposure to pathogenic Vibrio species.

Combination of Multilocus Sequence Typing and GS-PCR Reveals an Association of Pandemic Vibrio parahaemolyticus Clone with Clinical and Seafood Isolates

Vibrio parahaemolyticus is a global leading cause of seafood-borne bacterial gastroenteritis. Clinical, seafood, and environmental V. parahaemolyticus isolates from the eastern coast of China were analyzed for their virulence, and for phenotypic and molecular traits. The frequency of pandemic isolates was 50.9% among clinical isolates and 42.8% among seafood isolates as confirmed by group-specific polymerase chain reaction (GS-PCR). Serological analysis indicated that O3:K6, O1:K25, O1:KUT, O3:K68, and O4:K68 were the predominant serotypes among these pandemic isolates. It is worth noting that the pandemic serotypes were not exclusively identified from clinical samples. Rather, they were also isolated from seafood samples. It was also shown by multilocus sequence typing (MLST) typing that isolates from clinical (59), seafood (28), and environmental samples (18) were grouped into 17, 23, and 17 sequence types (STs), respectively. We updated 17 STs in the MLST database. ST-3 and ST-189 were the dominant ones among clinical isolates. Interestingly, ST-3 was also the most abundant among seafood isolates, and represented a significant risk to food safety due to the clear association with tdh and the GS-PCR marker. A minimum-evolution (ME) tree generated from the concatenated sequences of the 7 loci of the 54 STs uncovered phylogenetic relationships between seafood and clinical isolates. The MLST results also indicated a high degree of nucleotide diversity in recA that had the greatest influence on the phylogenetic relationships. Our findings provided new insight into the phylogenic relationship among pandemic V. parahaemolyticus isolates from various samples and enhanced the MLST database as well as microbiological risk assessment.

PRACTICAL APPLICATION

Pandemic V. parahaemolyticus isolates have become a serious public health concern. This study demonstrated the characteristics of clinical and seafood V. parahaemolyticus isolates, and determined the phylogenetic relatedness among them. These results can be used for microbiological risk assessment in China.

Characterizing the Adherence Profiles of Virulent Vibrio parahaemolyticus Isolates

The human pathogen Vibrio parahaemolyticus is a leading cause of seafood-borne illness in the USA, and infections with V. parahaemolyticus typically result from eating raw or undercooked oysters. V. parahaemolyticus has been shown to be highly resistant to oyster depuration, suggesting that the bacterium possesses specific mechanisms or factors for colonizing oysters and persisting during depuration. In this study, we characterized eight different V. parahaemolyticus strains for differences in resistance to oyster depuration, biofilm formation, and motility. While each strain exhibited distinct phenotypes in the various assays, we determined that biofilm formation on abiotic surfaces, such as glass or plastic, does not directly correlate with bacterial retention in oysters during depuration. However, we did observe that the motility phenotype of a strain appeared to be a better indicator for persistence in the oyster. Further studies examining the molecular mechanisms underlying the observed colonization differences by these and other V. parahaemolyticus strains may provide beneficial insights into what critical factors are required for proficient colonization of the Pacific oyster.

Seasonal effects of heat shock on bacterial populations, including artificial Vibrio parahaemolyticus exposure, in the Pacific oyster, Crassostrea gigas

During the warmer summer months, oysters are conditioned to spawn, resulting in massive physiological efforts for gamete production. Moreover, the higher temperatures during the summer typically result in increased bacteria populations in oysters. We hypothesized that these animals are under multiple stresses that lead to possible immune system impairments during the summer months that can possibly lead to death. Here we show that in the summer and the fall animals exposed to a short heat stress respond similarly, resulting in a general trend of more bacteria being found in heat shocked animals than their non-heat shocked counterparts. We also show that naturally occurring bacterial populations are effected by a heat shock. In addition, oysters artificially contaminated with Vibrio parahaemolyticus were also affected by a heat shock. Heat shocked animals contained higher concentrations of V. parahaemolyticus in their tissues and hemolymph than control animals and this was consistent for animals examined during summer and fall. Finally, oyster hemocyte interactions with V. parahaemolyticus differed based on the time of the year. Overall, these findings demonstrate that seasonal changes and/or a short heat shock is sufficient to impact bacterial retention, particularly V. parahaemolyticus, in oysters and this line of research might lead to important considerations for animal harvesting procedures.

Antibiotic resistance and molecular typing of Photobacterium damselae subsp. damselae, isolated from seafood

AIM

The objectives of our study is to determinate the antibiotic susceptibility of this organism to different antibiotics to determine the discriminatory power of the molecular typing methods.

METHODS AND RESULTS

In this study, 50 Photobacterium damselae subsp. damselae isolates from Scomber australasicus and Rachycentron canadum were collected in Taiwan and their resistance to 15 different antimicrobial agents was determined. In addition, random amplification of polymorphic DNA (RAPD) and pulsed-field gel electrolysis (PFGE) were performed to study the epidemiology and clonal relationship of P. damselae subsp. damselae. The results showed that the 50 isolates generated 25 typeable profiles with multidrug resistance to 3-7 antimicrobials. The results also indicate that the RAPD and PFGE methods have high discriminatory power for molecular subtyping.

CONCLUSION

Photobacterium damselae subsp. damselae isolates from fish to examine for multidrug resistance to antimicrobials. RAPD and PFGE methods revealed the high discriminatory power for molecular subtyping and provided information that could be used for risk assessment of P. damselae subsp. damselae infections.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results may help in epidemiological investigations of P. damselae subsp. damselae and may be useful in controlling or treating P. damselae subsp. damselae infections in aquaculture and clinical therapy.

Characterization of Vibrio parahaemolyticus isolated from oysters and mussels in São Paulo, Brazil

Vibrio parahaemolyticus is a marine bacterium, responsible for gastroenteritis in humans. Most of the clinical isolates produce thermostable direct hemolysin (TDH) and TDH-related hemolysin (TRH) encoded by tdh and trh genes respectively. In this study, twenty-three V. parahaemolyticus, previously isolated from oysters and mussels were analyzed by PCR using specific primers for the 16S rRNA and virulence genes (tdh, trh and tlh) and for resistance to different classes of antibiotics and PFGE. Nineteen isolates were confirmed by PCR as V. parahaemolyticus. The tlh gene was present in 100% of isolates, the tdh gene was identified in two (10.5%) isolates, whereas the gene trh was not detected. Each isolate was resistant to at least one of the nine antimicrobials tested. Additionally, all isolates possessed the blaTEM-116 gene. The presence of this gene in V. parahaemolyticus indicates the possibility of spreading this gene in the environment. Atypical strains of V. parahaemolyticus were also detected in this study.

Genetic relatedness among tdh+ and trh+ Vibrio parahaemolyticus cultured from Gulf of Mexico oysters (Crassostrea virginica) and surrounding water and sediment

Pathogenic Vibrio parahaemolyticus (Vp) (tdh(+)/trh(+)) represent a small percentage of environmental Vp populations, and very little is known about this subpopulation. Repetitive extragenic palindromic PCR and multilocus sequence analysis revealed heterogeneity among 41 Vp containing thermostable direct hemolysin (tdh) and tdh-related hemolysin (trh) that were isolated from Mississippi coastal environments from October 2006 to April 2007. There was no source-specific sequestering in oysters, water, or sediment.